/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.yarn;

import org.apache.flink.annotation.VisibleForTesting;

import org.apache.hadoop.yarn.api.records.Resource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.Nullable;

import java.lang.reflect.Method;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * Looks up the methods related to org.apache.hadoop.yarn.api.records.Resource#setResourceInformation.
 * Only supported in Hadoop 3.0+ or 2.10+.
 */
class ResourceInformationReflector {

	private static final Logger LOG = LoggerFactory.getLogger(ResourceInformationReflector.class);

	static final ResourceInformationReflector INSTANCE = new ResourceInformationReflector();

	/** Class used to set the extended resource. */
	private static final String RESOURCE_INFO_CLASS = "org.apache.hadoop.yarn.api.records.ResourceInformation";

	/** Could be Null iff isYarnResourceTypesAvailable is false. */
	@Nullable
	private final Method resourceSetResourceInformationMethod;

	/** Could be Null iff isYarnResourceTypesAvailable is false. */
	@Nullable
	private final Method resourceGetResourcesMethod;

	/** Could be Null iff isYarnResourceTypesAvailable is false. */
	@Nullable
	private final Method resourceInformationGetNameMethod;

	/** Could be Null iff isYarnResourceTypesAvailable is false. */
	@Nullable
	private final Method resourceInformationGetValueMethod;

	/** Could be Null iff isYarnResourceTypesAvailable is false. */
	@Nullable
	private final Method resourceInformationNewInstanceMethod;

	private final boolean isYarnResourceTypesAvailable;

	private ResourceInformationReflector() {
		this(Resource.class.getName(), RESOURCE_INFO_CLASS);
	}

	@VisibleForTesting
	ResourceInformationReflector(String resourceClassName, String resourceInfoClassName) {
		Method resourceSetResourceInformationMethod = null;
		Method resourceGetResourcesMethod = null;
		Method resourceInformationGetNameMethod = null;
		Method resourceInformationGetValueMethod = null;
		Method resourceInformationNewInstanceMethod = null;
		boolean isYarnResourceTypesAvailable = false;
		try {
			final Class<?> resourceClass = Class.forName(resourceClassName);
			final Class<?> resourceInfoClass = Class.forName(resourceInfoClassName);
			resourceSetResourceInformationMethod = resourceClass.getMethod("setResourceInformation", String.class, resourceInfoClass);
			resourceGetResourcesMethod = resourceClass.getMethod("getResources");
			resourceInformationGetNameMethod = resourceInfoClass.getMethod("getName");
			resourceInformationGetValueMethod = resourceInfoClass.getMethod("getValue");
			resourceInformationNewInstanceMethod = resourceInfoClass.getMethod("newInstance", String.class, long.class);
			isYarnResourceTypesAvailable = true;
		} catch (Exception e) {
			LOG.debug("The underlying Yarn version does not support external resources.", e);
		} finally {
			this.resourceSetResourceInformationMethod = resourceSetResourceInformationMethod;
			this.resourceGetResourcesMethod = resourceGetResourcesMethod;
			this.resourceInformationGetNameMethod = resourceInformationGetNameMethod;
			this.resourceInformationGetValueMethod = resourceInformationGetValueMethod;
			this.resourceInformationNewInstanceMethod = resourceInformationNewInstanceMethod;
			this.isYarnResourceTypesAvailable = isYarnResourceTypesAvailable;
		}
	}

	/**
	 * Add the given resourceName and value to the {@link Resource}.
	 */
	void setResourceInformation(Resource resource, String resourceName, long amount) {
		setResourceInformationUnSafe(resource, resourceName, amount);
	}

	/**
	 * Same as {@link #setResourceInformation(Resource, String, long)} but
	 * allows to pass objects that are not of type {@link Resource}.
	 */
	@VisibleForTesting
	void setResourceInformationUnSafe(Object resource, String resourceName, long amount) {
		if (!isYarnResourceTypesAvailable) {
			LOG.info("Will not request extended resource {} because the used YARN version does not support it.", resourceName);
			return;
		}
		try {
			resourceSetResourceInformationMethod.invoke(
				resource,
				resourceName,
				resourceInformationNewInstanceMethod.invoke(null, resourceName, amount));
		} catch (Exception e) {
			LOG.warn("Error in setting the external resource {}. Will not request this resource from YARN.", resourceName, e);
		}
	}

	/**
	 * Get the name and value of external resources from the {@link Resource}.
	 */
	Map<String, Long> getExternalResources(Resource resource) {
		return getExternalResourcesUnSafe(resource);
	}

	/**
	 * Same as {@link #getExternalResources(Resource)} but
	 * allows to pass objects that are not of type {@link Resource}.
	 */
	@VisibleForTesting
	Map<String, Long> getExternalResourcesUnSafe(Object resource) {
		if (!isYarnResourceTypesAvailable) {
			return Collections.emptyMap();
		}

		final Map<String, Long> externalResources = new HashMap<>();
		final Object[] externalResourcesInfo;
		try {
			externalResourcesInfo = (Object[]) resourceGetResourcesMethod.invoke(resource);
			// The first two element would be cpu and mem.
			for (int i = 2; i < externalResourcesInfo.length; i++) {
				final String name = (String) resourceInformationGetNameMethod.invoke(externalResourcesInfo[i]);
				final long value = (long) resourceInformationGetValueMethod.invoke(externalResourcesInfo[i]);
				externalResources.put(name, value);
			}
		} catch (Exception e) {
			LOG.warn("Could not obtain the external resources supported by the given Resource.", e);
			return Collections.emptyMap();
		}
		return externalResources;
	}

	/**
	 * Get the name and value of all resources from the {@link Resource}.
	 */
	@VisibleForTesting
	Map<String, Long> getAllResourceInfos(Object resource) {
		if (!isYarnResourceTypesAvailable) {
			return Collections.emptyMap();
		}

		final Map<String, Long> externalResources = new HashMap<>();
		final Object[] externalResourcesInfo;
		try {
			externalResourcesInfo = (Object[]) resourceGetResourcesMethod.invoke(resource);
			for (int i = 0; i < externalResourcesInfo.length; i++) {
				final String name = (String) resourceInformationGetNameMethod.invoke(externalResourcesInfo[i]);
				final long value = (long) resourceInformationGetValueMethod.invoke(externalResourcesInfo[i]);
				externalResources.put(name, value);
			}
		} catch (Exception e) {
			LOG.warn("Could not obtain the external resources supported by the given Resource.", e);
			return Collections.emptyMap();
		}
		return externalResources;
	}
}
